1. Field of the Invention
This invention relates to a continuous mixer with an improved mixing ability.
2. Description of the Prior Art
For mixing high molecular weight substances like synthetic resins, there have been known and used continuous type mixers which continuously mix and discharge feed materials. Of the continuous mixers, the duplex type which has a pair of parallel mixing shafts within a chamber is favored over the single type for its superiority in shearing and melting, and its mixing efficiency, resulting in a shorter mixing time.
In a mixing operation by the duplex type continuous mixer, however, there sometimes occurs the so-called short-pass phenomenon, whose occurrence depends upon the kinds of the mixing materials used, such as synthetic resins, or on the mixing ratio, the short-pass phenomenon allowing unmelted materials to pass through the mixer without undergoing shearing work. With the conventional continuous mixers of the above-mentioned type, it is difficult to prevent the short-pass phenomenon, so that there is always a possibility that unmelted material is mixed into and discharged along with melted material without the unmelted material undergoing sufficient mixing, thereby impairing uniform mixing and lowering the quality of the resulting product.